Ophthalmic surgery saves and improves the vision of tens of thousands of patients every year. However, given the sensitivity of vision to even small changes in the eye and the minute and delicate nature of many eye structures, ophthalmic surgery is difficult to perform and the reduction of even minor or uncommon surgical errors or modest improvements in accuracy of surgical techniques can make an enormous difference in the patient's vision after the surgery.
One type of ophthalmic surgery, vitreoretinal surgery, encompasses various delicate procedures involving internal portions of the eye, such as the vitreous humor and the retina. Different vitreoretinal surgical procedures are used, sometimes with lasers, to improve visual sensory performance in the treatment of many eye diseases, including epimacular membranes, diabetic retinopathy, vitreous hemorrhage, macular hole, detached retina, and complications of cataract surgery, among others.
During vitreoretinal surgery, an ophthalmologist typically uses a surgical microscope to view the fundus through the cornea, while surgical instruments that penetrate the sclera may be introduced into the surgical field to perform any of a variety of different procedures (FIG. 1A). The surgical microscope provides imaging and optionally illumination of the fundus during vitreoretinal surgery. The patient typically lies supine under the surgical microscope during vitreoretinal surgery and a speculum is used to keep the eye exposed. Depending on a type of optical system used, the ophthalmologist has a given field of view of the fundus, which may vary from a narrow field of view to a wide field of view that can extend to peripheral regions of the fundus. For many types of vitreoretinal surgery using the surgical microscope, the surgeon may desire to have a very wide field of view of the fundus that extends beyond the equator and even out to the ora serrata.
Many such systems use a primary lens, such as an indirect lens, that inverts a portion of the image of the surgical field seen by the surgeon. Absent further correction, this type of system provides the surgeon an inverted view of the ends of the instruments in the surgical field (FIG. 1B). The surgeon must mentally correct the view in order to move the instruments properly. Such mental corrections are difficult to perform and negatively impact surgical outcomes in many instances. To render the situation even more difficult, most systems also provide the surgeon with a view of an area of the eye outside of the indirect lens field. In this area, the bodies of the surgical instruments are oriented correctly (FIG. 1B).
To at least render the ends of the surgical instruments as they are actually positioned, many systems, such as stereo digital inverters, contain an inverter lens or perform digital image processing that further inverts the image of the surgical field. This results in the ends of the surgical instruments being portrayed accurately within the surgical field, but portions of the image that were not previously inverted then become inverted, again resulting in a disconnect between the bodies of the surgical instruments in part of the surgical field, and the ends of the instruments. The resulting image (FIG. 1C), as compared to the actual location of the instruments (FIG. 1A), can be seen by comparing FIG. 1A and FIG. 1C. Although this type of image requires less mental correction by the surgeon, the inverted portrayal of part of the bodies of the instruments is distracting and requires mental correction. As a result, surgical outcomes are still negatively impacted in many instances.